Friday, December 17, 2010

BLAMING CONTINENTAL FOR CONCORDE CRASH

In December 2010, a French court decided that Continental Airlines is
criminally responsible in the crash of the Concorde, back in summer
2000, which killed 113 people. Namely, a Continental plane, taking
off just minutes earlier, left a piece of debris on the runway, which
afterwards punctured the tire of Concorde and lead to the crash.

Should we blame Continental for this crash? Briefly, I believe we
should, but just a little.

Events have a large number of causes. In case of Concorde crash,
those include the design of the airplane (which was vulnerable to the
tire bursting at high speed), the related testing and certification
process (which was unable to identify that problem), the plane
operators (who did not strengthen the plane despite of numerous
similar incidents), the airport in Paris (which could not spot the
piece of metal on the runway), and the Continental plane, which
left the debris. In a sense, all of them are somewhat responsible.

Unfortunately, causality itself is a tricky concept as well. What is
needed for an act to be a cause for something? Perhaps I am guilty
if my act was necessary and sufficient to lead to an undesirable
outcome. If a soccer player kicks the ball, and the goalkeeper blocks
it, and the ball bounces to a window -- who is guilty? Both the kick
and the blocking were necessary, but not sufficient. The Concorde
case is similar: wrongly repaired thrust reverser was necessary but
not sufficient for the accident.

To overcome this paradox, we need a more complex concept of
responsibility. As the court ruled for 70% of the compensation claims
to be paid by Continental, it implicitly stated that the Continental
was to be blamed for about 70% of the crash. I believe this is the
right way to think about similar cases (although I would go for a
smaller percentage here). There are many culprits, but they are of
different importance. It was a shared responsibility where
Continental had a (minor) part.

Is there a consistent way to establish one's "share of blame"? I
doubt it. But we may still try.

First, it is not acceptable that a departing plane drops large pieces
of metal on the runway. Second, for years Air France knew the
problems with bursting tires and potential damage it caused. However,
little was done. This is unacceptable as well. One might propose
something along the following lines: First, calculate what is the
expected cost for the other airlines (including eventual crashes) if a
plane drops a piece of metal, given everyone follows the procedures
which was deemed appropriate in summer 2000 (call theses costs A).
Next, calculate how often would Concorde crash due to bursting tires,
using the procedures and technology as it was used by Air France
during the time of the crash, without any debris on the runway (call
related costs B). In total, A + B correspond to the sum of costs,
both of which are sufficient but not necessary for the accident. Now
find, what would be the second likelihood, given there is similar
debris on runway (call this C). The difference C - B corresponds to
the extra costs for Air France, caused by the debris, but also by the
weak design of the Concorde. The Continentals "guilt" might be (A +
1/2 (C - B))/(A + C), i.e. the costs Continental caused alone (A),
plus a half of the extra (1/2 (C - B)) as a percentage of the total
costs (A + C).

Although the the proposal above has many shortcomings, it helps to
analyse situations where there is no single ultimate "guilty" part.